MISSION 29P

What is Comet 29P?

This comet (aka 29P/Schwassmann-Wachmann 1) is the most observable that exists and yet we understand very little about it. The Comet Section has therefore launched this special project to ensure that our understanding of it is much improved such that it becomes the most observed comet that we know of.

This mysterious object is temporarily locked in its present near-circular orbit by the gravity of the giant planets, Jupiter and Saturn. Located at a mean heliocentric distance of 6.0 au, 29P describes an orbit around the Sun every 14.7 years or so, with a perihelion distance of 5.7 au and aphelion of 6.3 au. Because it never approaches the Sun closely, it never exhibits a distinctive tail, i.e. quite unlike most people’s idea of a comet. But like Jupiter and Saturn, the comet is observable during most of each year apart from the couple of months it spends in solar conjunction. Current location in the JPL Small-Body Database Browser.

So what can you do as an observer?

First if you want to capture images that can be used to perform photometry then do consult the Observing Tutorial.

Currently Richard Miles coordinates the observing campaign so please direct any queries to him. The main objectives are:

1. Detect any new outburst as soon as possible after it has taken place so that we can (a) determine the time of the event, and (b) initiate 'target of opportunity' images with the 2.0-m Faulkes Telescopes to study the resulting expanding coma.

2. Measure the brightness of the inner coma and determine (a) the maximum brightness of each outburst, and (b) follow its subsequent decline photometrically.

3. Establish a long-term archive of: (a) its photometric lightcurve (intensive observations began in 2014); (b) a high-precision astrometry archive (so its orbit is precisely known for the prediction of stellar occultations); and (c) archive images series depicting the development of the expanding coma after each significant outburst

By recording its characteristics in this way it is hoped that we can elucidate the true nature of this object

Current Status and Latest Observations:

!!! Strong outburst at 2021 January 14.04 +/-0.01  17.0R => 14.7R !!!

Mini-outburst at 2021 January 08.49 +/-0.22 16.93R => 16.80R

Mini-outburst at 2021 January 06.15 +/-0.06 16.95R => 16.75R

Mini-outburst at 2020 December 21.98 +/-0.08 16.70R => 16.50R

Mini-outburst at 2020 December 11.97 +/-0.07 16.35R => 16.10R

!!! VERY STRONG OUTBURST on 2020 November 19.763±0.001 from 16.2R to 13.2 R!!!

Thanks to Jean-François Soulier (L27, Haute-Provence, France) and Nick James (970, Chelmsford, UK) who independently discovered the comet going into outburst. Thanks to Nick's timely alert we have obtained the best coverage ever of one of this comet's outbursts. Here is a plot of the data from L27 showing the outburst lightcurve analysed in terms of the G magnitude using a 10" radius photometric aperture. A video of this outburst has been prepared by Jean-François.

Another outburst also took place less than 6 days later on 2020 November 25.45±0.24 with the magnitude going from 15.3R to 14.3R

29P reached opposition on November 6 and so has now entered the evening sky making it an excellent target for northern hemisphere observers. Located in Aries at a declination of +26 degrees, the comet will be readily visible all night between now and next March. Click on the thumbnail images below for a wide-field finder chart or a topocentric ephemeris of the comet's position up until 2021 Jan 31.

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Here below is the latest light-curve showing its activity during this apparition up until January 17. Click on the plot if you want to see the full-size image. There have been two very strong outbursts: one on July 26 and a second on November 19, minute-by-minute coverage of which we have achieved largely thanks to Jean-François Soulier's dedicated 29PREMOTE observatory. More on those findings later. Jean-François was also successful in catching the start of the August 22 event. In all we now have outburst lightcurves spanning the first few critical hours for FOUR events namely in 2017, 2019 and 2020(2).

In addition to strong outbursts, the nucleus has exhibited at least 16 mini-outbursts some of which have been so weak that there have been 5 instances where a large fraction of the ejecta have, after several days, fallen back onto the nucleus. This happens because the nucleus is very large (approx. 64 km across) and so has a relatively high gravity and high escape velocity (approx. 20-25 m/s). Our detailed observations are revealing this collapse of the inner coma - a behaviour unique to this body! We might indeed consider 29P not to be a comet but instead a unique Transition Object that was once a TNO.

Last 8-10 days' data in MPC format

(Date, RA, Dec, Magnitude, Observatory Code, Photometric aperture in arcsec, Comments)

List of Observers:

List of Observatory Codes / Observers / Instruments / Photometric aperture in arcsec

N.B. This is a comprehensive list of observatories/people whose work has contributed to the current Observing Campaign, which began in 2014 February.

203 G. Galli, S. Foglia Italy 0.36-m f/5.76 Schmidt-Cassegrain 5.5
204 L. Buzzi, A. Aletti Italy 0.36-m f/6.5 reflector 4.8/6.0; Italy 0.84-m f/3.5 reflector 5.6 
213 R. Naves, M. Campas Spain 0.30-m f/10 Schmidt-Cassegrain 10.0 square; Spain 0.30-m f/9 Schmidt-Cassegrain 5.4
323 P. Camilleri, J. Oey, R. Miles Australia 0.40-m f/5 reflector (Perth)
718 P. Wiggins Utah, USA 0.35-m f/7 Schmidt-Cassegrain 5.2
970 N. James England 0.28-m f/10 Schmidt-Cassegrain 5.2/5.8 check
A06 E. Cortes Spain 0.25-m f/3.6 Schmidt-Cassegrain 10.0 square
A77 J.-F. Soulier, F. Kugel France 0.20-m f/4 Newtonian reflector 5.0/6.6
B74 J. M. Bosch Spain 0.40-m f/10 Schmidt-Cassegrain 10.0 square
B96 E. Bryssinck Belgium 0.4-m f/3.8 astrograph 5.0
C10 J.-F. Soulier France 0.30-m f/3.8 Newtonian reflector 6.5, 4.9
C35 J. Aledo Spain 0.4-m f/3.4 Reflector 10.0 square

C42 Q. Ye (Zwicky Transient Facility) Xingming, China 0.50-m ?

C77 A. Mantero Italy 0.25-m f/4 Reflector 6.7
C90 L. Tremosa Spain 0.30-m f/5 reflector 10.0 square
E94 J. Drummond N.Zealand 0.35-m f/10 Schmidt-Cassegrain 5.9; 0.41-m f/5.2 Newtonian 7.2; 0.41-m f/4.5 Newtonian 6.0
G40 J. Tuten Canary Isles 0.43-m f/6.8 Dall-Kirkham 5.0
H06 N. James New Mexico 0.43-m f/4.5 5.8; A. Watkins New Mexico 0.43-m f/4.5 5.8
I41 Q. Ye (Zwicky Transient Facility) Palomar, USA 1.20-m f/2.5
I64 A. Jones England 0.19-m f/5.2 Mak-Newt + Rc filter 5.6
I81 D. Buczynski Scotland 0.35-m f/6 Schmidt-Cassegrain 5.2
I88 J. Carrillo Spain 0.36-m f/5 reflector 10.0 square
J01 J. Gonzalez Spain 0.15-m f/6 Ritchey-Chretien 10.0 square
J22 K. Hills La Palma 0.50-m f/2.9 astrograph 5.9, 10.0 square
J24 J. F. Hernandez Spain 0.4-m f/10 Schmidt-Cassegrain 10.0 square
J38 F. Garcia Spain 0.25-m f/8.1 Ritchey-Chretien 10.0 square
J47 G. Muler Lanzarote 0.30-m Schmdt-Cassegrain 6.1
J77 R. Miles England 0.35-m f/8 Schmidt-Cassegrain + r' 5.4 also V, B, Clear
K01 A. Watkins England 0.35-m f/7.7 Schmidt-Cassegrain 6.2
K02 P. Carson England 0.32-m f/5.4 Dall-Kirkham 5.5/6.5
K14 M. Morales Spain 0.25-m f/5 Newtonian 5.7, 10.0 square
L27 J.-F. Soulier France 0.20-m f/4 Newtonian reflector 6.5, 5.0
Q38 M. Mattiazzo Australia 0.28-m f/6.3 Schmidt-Cassegrain 5.5
Q67 P. Camilleri, J. Oey, R. Miles Australia 0.32-m F/8.8 RCOS 5.5
Q68 P. Camilleri, J. Oey, H. Williams Australia 0.30-m f/3.0 reflector 7.4; P. Camilleri, J. Oey Australia 0.34-m f/5.9 SCT
W88 K. Breedlove, J. Tuten, A. Hale Chile 0.35-m f/11 Schmidt-Cassegrain (Slooh) ???
W96 J.-F.Soulier, A.Maury, J.-B. de Vanssay Chile 0.4-m f/5.2 Ritchey-Chretien 6.4
Z08 E. Bryssinck Oria, Spain 0.70-m f/6 reflector (remote) 5.2 r'

Z10 P. Carson Spain 0.32-m f/5.4 Dall-Kirkham 5.5
Z30 D. Storey England 0.35-m Ritchey-Chretien 5.9
Z39 A. Acosta Lanzarote 0.23-m Schmidt-Cassegrain 10.0 square
Z42 J. Savage England 0.35-m f/7.7 Schmidt-Cassegrain + V 5.5, 7.9
Z74 F. Soldan Spain 0.20-m f/6.7 Schmidt-Cassegrain 10.0 square
Z80 G. Wells, D. Bamberger England 0.25-m f/8 Ritchey-Chretien 6.7
Z85 T. Angel Spain 0.35-m f/11 Schmidt-Cassegrain 5.6
XXX C.S. Morris California, USA 0.406-m f/6.8 Schmidt-Cassegrain 4.84

Las Cumbres Observatory / Faulkes Telescope Project (R. Miles, A. Hale):

A major contribution to this '24/7' comet monitoring activity have been the observations from the Las Cumbres Observatoryglobal network of telescopes. Access to this network has been made available thanks to the Dill Faulkes Education Trust, and to Dr Paul Roche of the Faulkes Telescope Project based at Cardiff University, Wales assisted by Alison Tripp.  

E10 coj 2m0a Siding Spring-FT South 2.0-m f/10 Ritchey-Chretien 5.4
F65 ogg 2m0a Haleakala-FT North 2.0-m f/10 Ritchey-Chretien 5.4

K91 cpt Sutherland A S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K92 cpt Sutherland B S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K93 cpt Sutherland C S. Africa 1.0-m f/8 Ritchey-Chretien 5.5

Q63 coj Siding Spring A Australia 1.0-m f/8 Ritchey-Chretien 5.5

Q64 coj Siding Spring B Australia 1.0-m f/8 Ritchey-Chretien 5.5
V37 elp McDonald Observatory A Texas, USA 1.0-m f/8 Ritchey-Chretien 5.5
V39 elp McDonald Observatory B Texas, USA 1.0-m f/8 Ritchey-Chretien 5.5
W85 lsc Cerro Tololo A Chile 1.0-m f/8 Ritchey-Chretien 5.5
W86 lsc Cerro Tololo B Chile 1.0-m f/8 Ritchey-Chretien 5.5
W87 lsc Cerro Tololo C Chile 1.0-m f/8 Ritchey-Chretien 5.5

L09 cpt Sutherland Aqawan A #1 S. Africa 0.4-m f/8 Ritchey-Chretien 5.7

Q58 coj Siding Spring Clamshell #1 Australia 0.4-m f/8 Ritchey-Chretien 5.7
Q59 coj Siding Spring Clamshell #2 Australia 0.4-m f/8 Ritchey-Chretien 5.7
T03 ogg Haleakala Clamshell #2 Hawaii, USA 0.4-m f/8 Ritchey-Chretien 5.7
T04 ogg Haleakala Clamshell #1 Hawaii, USA 0.4-m f/8 Ritchey-Chretien 5.7
V38 elp McDonald Obs. Aqawan A #1 Texas, USA 0.4-m f/8 Ritchey-Chretien 5.7
W79 lsc Cerro Tololo Aqawan B #1 Chile 0.4-m f/8 Ritchey-Chretien 5.7
W89 lsc Cerro Tololo Aqawan A #1 Chile 0.4-m f/8 Ritchey-Chretien 5.7
Z17 tfn Tenerife Aqawan A #2 Spain 0.4-m f/8 Ritchey-Chretien 5.7
Z21 tfn Tenerife Aqawan A #1 Spain 0.4-m f/8 Ritchey-Chretien 5.7

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Periodic outbursts, rotational period and outburst mechanism

A paper published in 2016 in the solar-system journal, Icarus, entitled "Discrete sources of cryovolcanism on the nucleus of Comet 29P/Schwassmann–Wachmann and their origin" identified a distinct periodicity of 57.71±0.06 d, which would correspond to the mean solar day on the nucleus given that outbursts are provoked by solar heating.

The orbital period of 29P is about 14.7 yr and now that we have reliable photometric data going to 2002 it is possible to construct a seasonal plot of the outbursts using the following ephemeris:

Rotational Phase = (Julian Date of Outburst - 2455229.98)/57.71

The following diagram provides a visual representation of the relative location of outbursts on the nucleus (assuming that Rotational Phase is related to Longitude) over time. Strong outbursts appear to be clumped in phase space indicating that these sources are located relatively close to each other or are repeat cryo-eruptions from the same cryovolcano. Weak outbursts have only been observed since 2014 - before that date low-level activity was overlooked by observers. Weak outbursts are also referred to as 'mini-outbursts' if their amplitude is <1.0 magnitude.

A unique feature of outbursts is their ability to trigger subsequent eruptions (as shown by the red lines). This behaviour is much more common amongst mini-outbursts and is believed to be associated with fall-back of ejecta that have not exceeded the escape velocity (~20 m/s). In the case of weak outbursts a much greater fraction of the ejecta falls back onto the nucleus in this way and serves to reform the surface and strengthen the crust so that it can hold a significant sub-crustal pressure. Consolidation of newly-fallen dust and debris takes place during the long nights on the nucleus when the temperature gradient near the surface reverses. It is this sub-surface pressure that stabilises cryomagma (probably a mixture of mainly methane/ethane/propane) and allows gases such as CO and N2 to dissolve in it. Where the crust gives way such as at a vent, cryomagma escapes into space accelerated by the 'exsolution' of dissolved gases leading to rapid cooling at the vent and the liquid hydrocarbons freeze to form a waxy solid sealing off the vent. The theory behind this proposed mechanism was published in the paper entitled, "Heat of solution: A new source of thermal energy in the subsurface of cometary nuclei and the gas-exsolution mechanism driving outbursts of Comet 29P/Schwassmann–Wachmann and other comets".

Outburst Video

Below is a video made from a series of some 57 images taken with 1.0-m telescopes of the Las Cumbres Observatory network over a two-month period showing an outburst that began on 2018 August 01 and which brightened from magnitude 16.5R to reach magnitude 14.2R within just a few hours. The field of view is about 2 arcminutes square. If necessary, to see the animated video clip, right click on the image and select 'Open image in new tab' then open the new tab.

Data Archive:

2020-2021 Apparition observations

2009-2020 2.0-m Astrometry